I've tried that POC in a shop and it just didn't feel comfortable. Dainese stuff is really breathable but very expensive for the protection it offers and they aren't very durable in my experience. The rivets/poppers that hold the plates to the padding and vest seem to fail after a bit of abuse.
D30 stuf performs well in tests, even when compared to rigid armour. I use products (Forcefield) that use D30 inserts on the elbow and shoulder and they're the best I've used for this so far. However, their back protectors are thick, heavy and not very breathable; fine when its cold but I wouldn't want to wear one hiking the pipe in Spring.
I use a back protector aimed at the motor bike market and its the best I've tried so far. Its by a German company called Held and this is the specific model I use:
http://www.getgeared.co.uk/HELD_9882_Motorcycle_Back_Protector_Waistcoat?sc=51&category=432573
It uses highly viscoelastic/shape memory foam. Like POC they don't make the padding themselves, they just put it in their products. Its a lot cheaper than the POC version, very comfortable and has great coverage of other vulnerable areas like the portion of your ribs directly below your shoulder socket, kidney etc...Its also less breathable than Dainese stuff but seem better than D30 based back protecots for ventilation and comfort.
I'd recommend looking at reviews in some motor bike magazines; these guys take their testing very seriously and actually look into the test results for the armour. Marketing is has its place when it comes too body armour buts it how the product performs under impact, reflected by lab results, which is going to determine whether its going to save your ass or not.
